[SI-LIST] Re: Why return current is directly under the signal trace?
- From: Doug Brooks <dbrooks9@xxxxxxxxxxxxxxx>
- To: nithin-bharadwaj@xxxxxxx,"kbmanick@xxxxxxxxx" <kbmanick@xxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 17 Apr 2013 07:50:08 -0700
With all due respect, this is not (at least directly) related to skin
effect at all.
But within the topic of skin effect, there are effects called the
"Proximity Effect": and the "Ground Effect." THESE effects are caused
by exactly the same phenomenon that causes the return path to be
directly on the plane directly underneath the trace: that is the
point of lowest mutual inductance.
The skin effect IS caused by inductance, but is not related to the
return current path,
I have a chapter on the skin effect in my forthcoming book "PCB
Currents: How They Flow, How They React" (Prentice Hall) due out on
5/17/13. I will have a blurb on it posted on the UltraCAD web pages
by the end of the week.
Doug Brooks
At 07:01 AM 4/17/2013, O Nithin Bharadwaj wrote:
>Hi Bala,
>
>This is a resultant of skin depth phenomenon. Lower the frequency,
>higher will be the penetration capability of charges in a conductor
>and higher the frequency lower will be the penetration area. For
>microstrip TL case, the current distribution will be spread to a
>larger area beneath the trace when compared with that of higher
>frequencies. This link below may give you better insight.
>
>http://www.rfcafe.com/references/electrical/skin-depth.htm
>
>Warm regards,
>Nithin
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Balamanikandan K
>Sent: Wednesday, April 17, 2013 5:58 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Why return current is directly under the signal trace?
>
>Hi,
>The return current for the high speed part of the signal will take
>the path of least inductance. At high speeds, return current stays
>tightly bunched under signal trace. Why is this directly beside the
>signal? Please explain.
>
>--
>Best Regards,
>Balamanikandan.K
>
>
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